Cancer refers to abnormal and uncontrolled cell growth and is one of the main causes of mortality worldwide. Conventional treatments comprises chemotherapy or radiation with lack of selectivity for cancer cells, causing deleterious damage to healthy cells and tissues due to their indiscriminating action, toxicity towards vital organs and severe inflammatory response due to necrosis.
Selectivity of therapeutic agents towards cancerous cells can be improved by conjugating the anticancer drugs with specific cancer targeting ligand such as tumor targeting peptides, antibodies.
Breast cancer accounts for one of the major causes of death in women. Chemotherapy, radiation, and hormonal therapy used to treat breast cancer, are all associated with severe side effects and lack tumor targeting specificity.
Some decapeptides (SEQ ID NO: 9: WLEAAYQKFL), with different residues at X positions have been found to have specific affinity to breast cancer cell lines. One of these peptide analogs conjugated with standard anticancer drug doxorubicin induced the selective effect against breast cancer than standard drug alone.
Temporins are antimicrobial peptides having 10 to 14 amino acids, isolated from skin secretions of amphibians. The temporin SHa (SEQ ID NO: 1: F-L-S-G-I-V-G-M-L-G-K-L-F) was identified as a potent inhibitor of bacteria, yeasts, fungi, and protozoa, as well as antiparasitic activity against promastigote and the intracellular stage (amastigote) of Leishmania infantum. Lysine-substituted analogs of temporin SHa such as [K3] temporin-SHa showed more potent antimicrobial activity than temporin-SHa, while L-alanine substituted analogs lack the antibacterial and antiparasitic activity. According to literature report, [K3] temporin-SHa and temporin-SHa exhibited low cytotoxicity (human erythrocytes, THP-1 monocytes and THP-1-derived macrophages) or no cytotoxicity (HepG2 cells and fibroblasts). While, L-alanine substituted analogs [A2,6,9] SHa and [A2,6,9, K3] SHa were inactive on THP-1 monocytes and HepG2 cells.
Antimicrobial peptides such as temporin-10Ea also demonstrated anticancer activities. Previous studies reported necrosis as a mode of cell death induced by some antimicrobial peptides, caused by the direct interaction of peptides to the plasma membrane resulting in the production of reactive oxygen species, leakage of calcium ions and rapid decrease in mitochondrial membrane production.
In order to meet with the demand of developing new and selective anticancer drugs with no adverse effects on other vital organs or tissues, we developed five new anticancer D-alanine substituted analogs (SEQ ID NOs 2-6) of temporin-SHa along with two anticancer peptide conjugates. The conjugate 7 was developed by linking a new anticancer analog (SEQ ID NO: 4) with a breast cancer targeting peptide, while conjugate 8 was obtained by conjugating the dimeric form of SEQ ID NO: 4 with cancer targeting ligand.